2017

November 2017: Sven Egenhoff

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Sven Egenhoff | Colorado State University

What is so Special about Shales? Concepts, Questions, and Problems (and, a Few Answers)

Abstract:

Black shales are important source rocks and unconventional  reservoirs for hydrocarbons, mostly gas, but also oil. However, it is still unclear which parameters control their formation, how their internal make-up relates to the updip depositional system, the sequence stratigraphy of shales, as well as their diagenesis. Originally,  black shales were thought to have formed in anoxic settings because of their high TOC contents that were seen as an indicator of a lack of free oxygen. Nevertheless, sedimentary  structures in shales such as ripple  foresets and ripple  trains argue for at least episodic water movement  that could have replenished shale environments  with oxygen, and fecal strings and burrows also speak for at least to a degree oxygenated conditions  during sedimentation.  Based on observations from the Recent it is speculated that most organic matter is transported as marine snow particles through an oxic water column to the ocean floor. In this model, the inner part of marine snow particles is envisioned to protect organic matter from oxidizing.  Diagenesis in shales is turning out to be complex with, in case of the Bakken (Williston  Basin) and Tøyen (Scandinavia) shales, multiple  pyrite, quartz and carbonate generations present. Surprisingly,  the upper Bakken shale in North Dakota shows two carbonate generations as the earliest cement phases that point to an oxygenated depositional and earliest diagenetic environment.  Sequence stratigraphy in shales is based on stacking patterns of different shale facies. In the case of the upper Bakken shale in North Dakota, this unit can be subdivided  into two stratigraphic  intervals with the lower one representing transgressive, and the upper regressive conditions.  Detailed correlations show that a part of the upper Bakken shale is likely  equivalent to the overlying  Lodgepole carbonates and does not represent a completely independent unit as previously assumed.

Biography:

Sven was born in Germany, and raised in Germany, Iran, and Argentina which helped shape his career path as a geologist. After finishing high school in Buenos Aires, Argentina, Sven studied at the University of Clausthal for his undergraduate degree, and obtained his Diploma (equivalent to a Masters' degree) from Heidelberg University, Germany, on a field study in the breathtaking Italian Dolomites. Moving to Technische Universität Berlin, Germany, Sven received his PhD in 2000 for a study on basin analysis in southern Bolivia. After a five year lecturer position at Technische Universität Bergakademie Freiberg in south-eastern Germany, he accepted the position as Assistant Professor at Colorado State University in 2006, was promoted to Associate Professor in 2010, and to Full Professor in 2016. Sven’s areas of expertise are understanding sedimentary processes in carbonates and shales, and applying resulting depositional models to better characterize oil and gas reservoirs.

October 2017: Steve Cumella

Steve Cumella | Consultant to Whiting

Fun Things to Do with Digital Logs in Your Spare Time

Abstract:

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Robust digital-log datasets allow the subsurface to be creatively imaged using cross sections with single-track color-filled log displays. Furthermore, simple processing of a log can reveal interesting data content not readily visible in normal log displays. For example, the large-scale depositional architecture of sedimentary sequences can be seen in cross sections constructed from gamma-ray logs smoothed over intervals of a hundred feet or so. Another example is using the first derivative of the temperature curve to reveal subtle changes in gradient that result from different thermal conductivities of rocks and the fluid in the rocks. Neutron-log cross sections can indicate gas bearing horizons. Resistivity cross sections can show resistivity reversals that indicate the transition from wet to dry gas. Sonic log cross sections can indicate the presence of overpressured parts of a basin. And the list goes on.

The smoothed gamma-ray cross section of the Mesaverde in the southern Piceance Basin shown below is constructed from hundreds of smoothed gamma-ray logs along four different line-and-corridor segments. Warm colors are low gamma ray. The bright-red marine shorefaces in the lower right prograded during times of low accommodation. These intervals can be traced landward to amalgamated fluvial channel sandstones that are also the result of periods of low accommodation. The low net-to-gross interval in the middle of the cross section acts as a top seal to the Mesaverde gas accumulation in much of the southern Piceance.

biography:

Steve Cumella is a consulting geologist in Denver, Colorado, working primarily for Whiting since 2014. He received his bachelors and masters in geology at University of Texas at Austin and started his career with Chevron in 1981. Steve worked the Piceance Basin and other Rocky Mountain basins at Barrett Resources, Williams, Bill Barrett Corporation, and Endeavour International. He was awarded Rocky Mountain Association of Geologists’ Outstanding Scientist Award in 2005 and AAPG’s Robert H. Dott, Sr. Memorial Award for Best Special Publication in 2010. He was an AAPG Distinguished Lecturer in 2011. He is past executive editor of the Mountain Geologist and was president of the Grand Junction Geological Society in 1991. Steve has authored several publications, given numerous presentations, and led several fieldtrips.

September 2017: Ali Jaffri

Ali Jaffri | Applied Stratigraphix

Our Belief in Benches; Will it Ever Go Away? A Sequence Stratigrapher's Perspective on Layer-Cake Stratigraphy

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abstract:

Exxon made sequence stratigraphy mainstream almost forty years ago. Almost every asset-team geoscientist has probably seen the drastically different results produced from lithocorrelation versus chronocorrelation of well logs. Despite knowing this, we as an industry continue to perpetuate the myth of layer-cake stratigraphy. The focus on unconventional resource plays has made the use of benches more rampant than ever before. This presentation covers some reasons why we continue with practices that we know are inherently wrong. Through real-world examples from clastic and carbonate reservoirs, this talk focuses on why it has become increasingly important to correlate logs in a manner that is most conducive to delineating reservoir geometry.

biography:

Dr. Ali Jaffri has over eighteen years of experience in sedimentology and stratigraphy projects that range from leading geology field trips, seismic stratigraphy for prospect evaluation, facies geomodeling, and description of over 3 kilometers of core on a cm-scale. He has expertise on a variety of basins including the North Sea, Lower Indus Basin, Barents Sea, Offshore East and West Africa, Taranaki Basin, Offshore Mid-Norway, Kohat-Potohar Basin and several US onshore basins. Dr. Jaffri is equally proficient in carbonates and siliciclastics because his doctoral dissertation focused on the sequence stratigraphy of mixed systems. In 2012, Dr. Jaffri founded Applied Stratigraphix, which in just five years has a client base that comprises of 27 companies from majors to small independents across the globe.

April 2017: Chris Laughrey

Chris Laughrey | Weatherford Labs

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Petroleum Geochemistry and Mudstone Diagenesis of the Woodford Shale, Anadarko Basin, USA – An Integrated Approach

abstract:

We undertook an integrated organic geochemical and petrologic study of the Upper Devonian-Lower Mississippian Woodford Shale on cores recovered from thermally mature and liquids-rich mudstone reservoirs in the Anadarko basin of south-central Oklahoma, USA. The purpose of the work was to identify the critical mechanisms that control oil and natural gas generation, expulsion, migration, and retention in an active petroleum source rock that is also a producing unconventional reservoir.

We identified five microfacies in the Woodford Shale; 1) siliceous mudstone; 2) silicified mudstone; 3) chert and argillaceous chert; 4) argillaceous, siliceous dolostone; and 5) phosphatic mudstone. All of these microfacies exceed the minimum TOC and S2 threshold values for effective petroleum source rocks. The original HI values, calculated from visual kerogen data, indicate oil-prone organic matter in the rocks. Thermal maturity approximates the boundary between low-volatile and high-volatile liquid generation. Maximum burial temperatures were between 124 to 134°C. Sixty to 75 % of the petroleum generation process is complete and expulsion efficiency was 61 to 83 %. Plots of oil crossover effect and oil saturation indices denote Woodford Shale intervals that retained adequate volumes of hydrocarbons for commercial petroleum production.

Reservoir quality in these productive intervals is controlled by the diagenetic fabric of the mudstones. Mineral matrix porosity was reduced by compaction, quartz cementation, and bitumen expulsion from kerogen during deeper burial. However, significant mineral matrix porosity was initially preserved in microfacies that underwent early quartz cementation, and relatively larger amounts of pre-oil bitumen filled these spaces prior to the onset of petroleum generation and organic-matter porosity formation. Organic-matter porosity now comprises greater than 99 % of the observed pore volume, and occurs within an extensive and well-connected post-oil solid bitumen network which serves as a major petroleum migration path.

biography:

Christopher D. Laughrey is a Senior Petroleum Systems Analyst with Weatherford Laboratories’ Geochemical Interpretive Services (OilTracers) Group. His forty years of professional experience is international in scope with specializations in isotope and petroleum geochemistry, production monitoring and allocation of petroleum and water, clastic and carbonate reservoir petrology, basin analysis, and geophysical log interpretation. Christopher consults for private industry working on integrated interpretive projects, teaches workshops on both unconventional and conventional reservoir geology and geochemistry, and collaborates with other Weatherford scientists on research and business development efforts within the company. Prior to joining the OilTracers group in 2016, Christopher worked for a year with the Dolan Integration Group in Boulder, Colorado, and for five years as a Senior Geosciences Advisor for Weatherford Laboratories in Golden, Colorado. At Weatherford, he focused on unconventional resources in various Rocky Mountain basins, the Anadarko and Arkoma basins, and the Appalachians. He also completed projects in various other basins in the United States, Canada, Australia, China, Argentina, Colombia, the Middle East, Russia, and new plays in the UK. He was involved in Weatherford Laboratories’ research and development efforts in quantitative natural gas isotope applications in the petroleum geosciences, high-resolution SEM imaging and 3-D modeling of low-permeability fine- grained clastic and carbonate reservoirs with an emphasis on the evolution of organic and inorganic pore systems, biomarker applications in petroleum resource systems, and high-temperature programmed pyrolysis of organic matter in unconventional shale-gas and tight-oil reservoirs. Christopher has conducted numerous professional workshops in applied shale petrology, petroleum geochemistry, sequence stratigraphy, and carbonate petroleum reservoirs for the Petroleum Technology Transfer Council, AAPG, SPE, and numerous oil and gas companies including Cabot, Chevron, Colombian Petroleum Institute, El Paso, ExxonMobil, Hess, Petro China, Repsol, Shell, and Talisman. In 2008 and 2009, Christopher conducted Carbonate Petroleum Reservoir workshops and field seminars for Petro China through Geologic Mapping and Resource Evaluation (GMRE), Inc.in State College, Pennsylvania. From 1980 through 2009, Christopher worked as an industry consultant, and as a Senior Geological Scientist for the Pennsylvania Geological Survey where he conducted applied research in tight-gas sands, fractured carbonate reservoirs, applied sequence stratigraphy, shale petrology, source rock geochemistry of the Marcellus and Utica shales, and natural gas isotope geochemistry throughout the Appalachian basin. Christopher taught graduate courses in sandstone and carbonate petrology and undergraduate geochemistry at his alma mater, The University of Pittsburgh. He is the author or coauthor of forty technical papers and books on the application of integrated geochemistry, petrology, and stratigraphy to petroleum exploration and production, and on the applications of isotope geochemistry to the mitigation of stray natural gas environmental problems. Christopher began his career in 1977 as a geologist and geophysical analyst for the Marine Seismic Exploration Department at the Western Geophysical Company (now Western Geco) in Houston, Texas.